Pigeon erythrocyte membrane material at three levels of disassembly will be fractionated by density gradient centrifugation and/or preparative IEF, and the protein compositions examined by high resolution 1- and 2-dimensional electrophoretic procedures. The 2-dimensional procedures are 1) IEF (denaturing) x SDS (denaturing), 2) IEF (non-denaturing) x SDS and 3) IEF (non-denaturing) x Ornstein-Davis (non-denaturing). Work will be begun on identification of some components. The three levels of disassembly are 1) small transport-active membrane vesicles, 2) small, dilute membrane-lipid hybrid vesicles and 3) solubilized membrane. The main aim is to detect specific associations between membrane proteins. Selected fractions of solubilized membrane will be assayed for recovery of Ca ions transport activity. Work will continue on identification and characterization of intermediate Mw substances, extractable from membranes, which modulate ATP-dependent Ca ions transport activity of membrane vesicles.